Screened igniter for ramjet burners



Jan. 31, 1961 J. w. MULLEN 11 2,969,643

SCREENED IGNITER FOR RAMJET BURNERS Filed Oct. 15, 1949 F I G. I

INVENTOR.

JAMES W. MULLEN II ATTORNEY United States Patent O 2,969,643 SCREENED IGNITER FOR RAMJET BURNERS James W. Mullen 11, Richmond, Va., assignor, by mesne assignments, to the United States of America as repre sented by the Secretary of the Navy Filed Oct. 13, 1949, Ser. No. 121,102 2 Claims; (Cl. 60-3911) The present invention relates to an improved igniter.

More specifically the invention relates to a flame igniter for use in the combustion chamber of a ram-jet engine.

In the operation of ram-jet engines it is highly desirable that proper burnin-g take place in the combustion chamber in order that the maximum possible thrust be developed by the engine with the greatest combustion efliciency. It is also necessary for the reason that, when improper burning occurs, unburned gases sometimes accumulate in the combustion chamber, thereby increasing the possibility of an explosion which could result in considerable damage to equipment as well as injury to operating personnel.

Investigation has established that proper combustion within the engine is mainly dependent on the manner in which the fuel-air mixture being burned is ignited and that proper ignition is in turn dependent upon several factors, all of which combine in their effect to produce improved combustion conditions at the point of ignition. One of such factors is the structure of the igniter assembly, the primary function of which is to bring about complete combustion in as short a time as is possible. In order that this be done it is essential that the air-fuel mixture be ignited throughout the full cross sectional area of the chamber in which it is being burned, under as ideal conditions as are reasonably attainable.

It is therefore one object of the present invention to provide an igniter, the use of which will result in improved burning in the combustion chamber of a ramjet engine.

Another object of the invention is to provide for improved combustion conditions at the point of ignition in the combustion chamber of a ram-jet engine.

A further object of the invention is to provide an improved igniter of simple and light construction for use in ram-jet engines, whereby more efficient performance of the engine can be obtained.

Other objects and many of the attendant advantages of this invention will be appreciated readily as the same becomes understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein:

Fig. l is a view in axial section, of a fragment of the combustion chamber of a ram-jet engine wherein the device constituting the present invention is mounted, said device itself being shown in perspective; and

Fig. 2 is a view similar to Fig. 1, but showing a modified igniter.

Broadly, the invention contemplates a screen mounted in the combustion chamber of a ram-jet engine in juxtaposition to a fuel injector nozzle, the combination acting upon the air-fuel mixture passing into the chamber to provide improved burning.

Referring now to the drawings, and more specifically to Fig. 1, a fragment of a ram-jet combustion chamber 1 is shown in which is mounted a container consisting of a cylindrical portion 2 and having a frusto-conical skirt 3 extending rearwardly from its downstream end. The container is supported in the chamber by a pair of pipes 4 and may house either a pilotflare or a pilot fuel burner, pilot fuel being supplied through pipes 4 and portion 2 to a pilot flame contained within skirt 3. At-

tached to the rim of the skirt 3 is an annular screen 6, which may be of any desired construction so long as it freely passes the combustible mixture to provide complete combustion, and which extends radially to the walls of the combustion chamber, and is secured thereto so as not to be blown away by the force of the air-fuel mixture passing through the chamber.

The structure of the igniter assembly shown in Fig. 2 is similar to that shown in Fig. 1, except for the relative positions of the screen 16 and the frusto-conical skirt assembly 12, 13, and 14. In the modification of Fig. 2, a disk-like screen 16 is mounted upstream from the point of ignition between fuel injector 17 and frustoconical skirt assembly 12, 13, and 14, so as to act upon the fuel-air mixture passing through the chamber before it reaches the frusto-conical skirt.

While a fuel-air burner is shown as the pilot in Fig. 1, and a flare instead in Fig. 2, it will be understood that these igniting means are equivalent and interchangeable, that is, either form of the invention may embody at will either the flare or the fuel-burning pilot. Obviously also, when a flare is used, the supports 14 need not be pipes, but could equally well be mere rods.

Referring again to Fig. 1, air is rammed through the combustion chamber in the direction indicated by the arrow and fuel is supplied thereto under pressure through a fuel injector 7 mounted upstream from the portion 2. The fuel is injected into the chamber in the form of a tine spray which mixes with the air being rammed through the chamber and is ignited by a pilot flame situated within skirt 3. Although it is not fully understood how screen 6 acts on this fuel-air mixture, it has been conclusively established that ignition across the full cross sectional area of the combustion chamber is achieved in a much smoother and more nearly complete manner than in any previous igniter.

In one specific embodiment of the invention, a No. 10 mesh stainless steel screen having a 56 percent open area was mounted in a two-inch diameter combustion chamber and was found to greatly improve the quality of burning therein.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A burner assembly comprising a conduit, means to supply fuel to said conduit, a container supported in said conduit downstream from said means, said container being outwardly flared to an opening at its downstream end, means producing a pilot flame within said container, and a screen fitting around and extending to the conduit wall substantially in the plane of said opening.

2. A burner assembly comprising a conduit, means to supply fuel to said conduit, a container substantially coaxially arranged in said conduit downstream from said means, said container being outwardly flared to an opening at its downstream end, means producing a pilot flame within said container, and an annular screen fitting against the inner wall of the conduit and also fitting around said container whereby the entire stream flows through the screen.

References Cited in the file of this patent UNITED STATES PATENTS 1,839,880 Hyatt Jan. 5, 1932 1,888,749 Urquhart Nov. 22, 1932 2,385,833 Nahigyan Oct. 2, 1945 2,508,420 Redding May 23, 1950 2,520,388 Earl Aug. 29, 1950 

